TOKYO (AP) — An underwater robot captured images of lava-like lumps Thursday inside a damaged reactor at Japan's crippled Fukushima nuclear plant, spotting for the first time what is believed to be nuclear fuel that melted six years ago.
Plant operator Tokyo Electric Power Co. said the robot found large amounts of lava-like debris, apparently melted fuel that flowed out of the core into the primary containment vessel of the Unit 3 reactor at Fukushima. The plant was destroyed by a massive earthquake and tsunami in March 2011.
Experts have said the fuel melted and much of it fell to the chamber's bottom and is now covered by radioactive water.
TEPCO spokesman Takahiro Kimoto said it was the first time a robot camera has captured what is believed to be the melted fuel.
"That debris has apparently fallen from somewhere higher above. We believe it is highly likely to be melted fuel or something mixed with it," Kimoto said.
In an earlier survey Wednesday, the robot found severe damage in the vessel but no signs of melted fuel.
Kimoto said the robot probe in its two missions has captured a great deal of useful information and images showing the damage inside the reactor, which will help experts eventually determine a way to remove the melted fuel, a process expected to begin sometime after the 2020 Tokyo Olympics.
"It's a big step forward," he said.
Locating the fuel in each of the three wrecked reactors is crucial for decommissioning the plant.
The robot, nicknamed "the Little Sunfish," went deeper on Friday into a structure called the pedestal for a closer look.
Experts have said the melted fuel is most likely to have landed inside the pedestal after breaching the core. It is believed to be covered by highly radioactive water as deep as 6 meters (20 feet).
The robot, about the size of a loaf of bread, is equipped with lights, maneuvers with five propellers and collects data with two cameras and a dosimeter. It is controlled remotely by a group of four operators. It was co-developed by Toshiba Corp., the electronics, nuclear and energy company charged with helping clean up the plant, and the International Research Institute for Nuclear Decommissioning, a government-funded consortium.